Authorities rule out some potential causes of Texas blast

By CNN Staff

Updated 10:46 AM ET, Tue May 7, 2013

Chat with us in Facebook Messenger. Find out what's happening in the world as it unfolds.

Photos:Photos: Texas fertilizer plant explodes

Texas fertilizer plant explodes – Forensic mappers work the crater at the site of a fire and explosion in West, Texas, on April 24, 2013. The West Fertilizer Co. plant in the small Texas town exploded days earlier on April 17, killing 15 people.

Hide Caption

1 of 20

Photos:Photos: Texas fertilizer plant explodes

Texas fertilizer plant explodes – Agents from the Bureau of Alcohol, Tobacco, Firearms and Explosives search the bank of rail tracks for evidence at the site of the explosion.

Hide Caption

2 of 20

Photos:Photos: Texas fertilizer plant explodes

Texas fertilizer plant explodes – Search and rescue workers comb through what remains of a 50-unit apartment building, in foreground, and a nursing home on April 18, 2013.

The investigation into the explosion will last longer than expected, the agency said. The probe was expected to be complete by May 10 but will extend another one to two weeks, the fire marshal's office said.

JUST WATCHED

Obama consoles devastated Texas town

MUST WATCH

JUST WATCHED

Reality star brings aid to West, Texas

MUST WATCH

Reality star brings aid to West, Texas01:09

Photos:West, Texas: A community mourns

Photos:West, Texas: A community mourns

West, Texas: A community mourns – U.S. President Barack Obama attends a memorial service at Baylor University in Waco, Texas, on April 25. The memorial was held for those killed in the blast at a Texas fertilizer plant. Fourteen people, nearly all first responders, died in an explosion at the West Fertilizer Co. on April 17. See photos from the explosion.

Hide Caption

1 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – Photos of the fallen firefighters stand next to their coffins at the memorial on April 25.

Hide Caption

2 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – Mourners at the memorial on April 25.

Hide Caption

3 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – Coffins containing the remains of victims from the fertilizer plant explosion in the town of West, Texas, at a memorial on April 25.

Hide Caption

4 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – A firefighters honor guard stands before the coffins of fallen comrades on April 25.

Hide Caption

5 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – Firefighters salute as fire trucks and emergency vehicles pass under a flag before the memorial service on April 25.

Hide Caption

6 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – Firefighters lead the funeral procession for Capt. Kenneth "Luckey" Harris Jr. on Thursday, April 24, in West, Texas.

Hide Caption

7 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – Firefighters stand on the back of a firetruck that transported Harris' body to the Bold Springs Cemetery in West on April 24.

Hide Caption

8 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – Family and friends stand in front of Harris' casket at the cemetery on April 24.

Hide Caption

9 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – A bugler plays taps at a memorial ceremony at the site of the explosion in West on April 24.

Hide Caption

10 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – Pallbearers carry the casket of fallen firefighter Capt. Kenneth "Luckey" Harris Jr. after his funeral at St. Mary's Catholic Church of the Assumption in West, Texas, on April 24.

Hide Caption

11 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – A memorial is set up on Monday, April 22, outside a fire station for the firemen who perished in the explosion.

Hide Caption

12 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – Flowers are tied on a firetruck on April 22 as a memorial for the firemen who died while responding to the explosion.

Hide Caption

13 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – Vanna Wainwright and her daughter Breanna take part in an open air Sunday service on April 21. Members of the First Baptist Church held their service in an open air field after their church was damaged from the explosion.

Hide Caption

14 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – Local residents attend a commemoration ceremony on April 21 for those that perished during the fertilizer explosion.

Hide Caption

15 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – Local residents attend a ceremony in West, Texas, on April 21.

Hide Caption

16 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – Residents embrace after a Sunday service at St. Mary's Catholic Church on April 21, four days after the deadly explosion.

Hide Caption

17 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – Residents collect donations on Saturday, April 20.

Hide Caption

18 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – A candlelight vigil is held at St. Mary's Catholic Church in West, Texas, on Thursday, April 18.

Hide Caption

19 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – Eric Garcia, 12, cries during a candlelight vigil in West, Texas, honoring the victims of the explosion on April 18. More than 200 people were injured and 50 homes destroyed in the small town.

Hide Caption

20 of 28

Photos:West, Texas: A community mourns

Photos: West, Texas: A community mourns – People gather for a candlelight vigil at a church in West on April 18.

Hide Caption

21 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – Residents tend a prayer service at St. Mary's.

Hide Caption

22 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – A girl closes her eyes during the vigil.

Hide Caption

23 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – A young mourner is comforted during the vigil on April 18.

Hide Caption

24 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – People pray during a candlelight vigil at St. Mary's Church on April 18.

Hide Caption

25 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – Residents embrace after taking part in the vigil.

Hide Caption

26 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – A woman clasps her hands during the candlelight vigil on April 18.

Hide Caption

27 of 28

Photos:West, Texas: A community mourns

West, Texas: A community mourns – A young man holds a candle during the vigil.

Hide Caption

28 of 28

Photos:West, Texas: Faces and places

Photos:West, Texas: Faces and places

West, Texas: Faces and places – Emil "Sonny" Fridel, 90, surrounds himself with memories of his late wife, Pearl -- including the oils, china plates and dolls whose faces she painted. Even after she died, he frequented the West Rest Haven nursing home where she spent her last days. He wanted to help the residents there the night of the fertilizer explosion.

Hide Caption

1 of 9

Photos:West, Texas: Faces and places

West, Texas: Faces and places – There's a touch of the Wild West in West. Witness the pickup of the town artist, Bobby Allen. The steer horns that peek out of the back will become his next canvas.

Hide Caption

2 of 9

Photos:West, Texas: Faces and places

West, Texas: Faces and places – Outsiders have responded to the disaster in West. The fair and rodeo grounds, site of the annual Westfest celebrating the town's Czech heritage, is the hub for donations from near and far. Separate from the food and the stacks of bottled water are clothes, toiletries, dishes, books, diapers, toys -- you name it.

Hide Caption

3 of 9

Photos:West, Texas: Faces and places

West, Texas: Faces and places – Edward Havel's colorful and clutter-filled Czech Point Collectibles & Antiques is a gathering place for West residents, where coffee fuels the conversation and pastries from the nearby Village Bakery soothe the soul. Havel brews 12 pots a day.

Hide Caption

4 of 9

Photos:West, Texas: Faces and places

West, Texas: Faces and places – Many stores in town bear the Czech greeting "Vitame Vas." The first settlers came to the area decades before West was formally established in 1882. The railroad brought outsiders, including Czech immigrants who in many ways still define the place.

Hide Caption

5 of 9

Photos:West, Texas: Faces and places

West, Texas: Faces and places – Petr Gandalovic, the Czech Republic ambassador to the United States, came to West to offer condolences on behalf of his country. He says the town's disaster is the No.1 news story there.

Hide Caption

6 of 9

Photos:West, Texas: Faces and places

West, Texas: Faces and places – Edward Havel's Czech Point is a collection of garage-sale finds, auction treasures and good old American kitsch.

Hide Caption

7 of 9

Photos:West, Texas: Faces and places

West, Texas: Faces and places – Folks in West don't know what to make of all the media, like this scrum at City Hall.

Hide Caption

8 of 9

Photos:West, Texas: Faces and places

West, Texas: Faces and places – Donna's House of Flowers is closed, and a note on the door explains the tragic reason: Her husband and brother-in-law, both volunteer firefighters, died in the explosion.

Hide Caption

9 of 9

Scores of investigators have followed up on 237 leads into the explosion. At least 60 investigators have been on site each day and conducted 411 interviews in trying to determine how the fire started and what caused the explosion.

The blast happened about 20 minutes after the first report of a fire at the fertilizer facility. It registered on seismographs as a magnitude 2.1 earthquake and could be felt 50 miles away.

The explosion damaged numerous homes, a nursing home and the town's high school and middle school, all of which were built within a few hundred feet of the plant.

West Fertilizer Co., which operated the facility, had been cited by federal regulators twice since 2006.

In 2012, the Transportation Department's Pipeline and Hazardous Materials Safety Administration fined West Fertilizer $5,250 for storing anhydrous ammonia in tanks that lacked the proper warning labels. The agency originally recommended a $10,000 penalty, but it was reduced after the company took corrective action.

In 2006, the EPA fined the company $2,300 to correct problems that included a failure to file a risk management program plan on time. The Texas Commission on Environmental Quality also investigated a complaint about the lingering smell of ammonia around the plant the same year.